A great view while it lasts Endangered shores: As sea level rises with global warming, erosion eats away cliffs, marshes, and people lose bay access.

RANDLE CLIFF BEACH -- Jonathan and Nanette Sheldon own what most Marylanders only dream about -- a house on the water, with a breathtaking view of Chesapeake Bay.

Perched atop an 80-foot cliff in this Calvert County community, the three-bedroom house looks down on passing freighters and geese in flight. On a clear day, you can see the Bay Bridge, more than 20 miles to the north.

But in years to come, the Sheldons' house on the water will be in the water. Bit by bit, such coveted waterfront home sites and ecologically rich marshland are vanishing all around the bay, the victims of shoreline erosion. Experts say such losses are likely to worsen if sea level rises as the Earth warms, as many scientists believe it will.

The Chesapeake's lapping waves nibble at the smooth base of the cliff on which the Sheldons' house sits, causing chunks of the clay wall to drop into the water. Their deck, built on solid land eight years ago, now juts three feet over the edge.

THe bluff may not give way for a decade or two, or it may happen much sooner depending on the frequency and severity of the storms that hit.

"We've just made up our minds we'll enjoy it as long as we can and just let it go," said Mrs. Sheldon.

Some would say risk comes with the territory, but people who don't own waterfront property also have reason to regret the rising sea level. Landowners' efforts to armor their shoreline against the battering waves are gradually depriving the public of access to the bay.

Scientists have been debating global warming for years, but increasingly the argument is over how bad it will be, not whether it will occur.

The Earth's average surface temperature has increased only about 1 degree Fahrenheit in the past century, but nine of the warmest years in that time have occurred since 1980, notes a new report by the Environmental Protection Agency.

Sea level has risen about a foot in the past century, which geologic evidence indicates is about three times faster than the rate of sea-level rise for the previous 5,000 years. About half of that increase came from land subsiding, or sinking, which may stem from ground water being pumped out because of development.

While that sea-level rise may not seem like much -- an inch or so every decade -- the loss of land can be dramatic in low-lying coastal areas. On the marshy lower Eastern Shore, the elevation in some places is less than a foot above sea level for up to a mile inland.

Scientists recently scaled back their predictions of how much the planet's temperature is likely to increase over the next century. They likewise moderated estimates of how much oceans may swell as glaciers melt.

The EPA, in a report released late last month, estimates that global temperatures are "most likely" to rise nearly 2 degrees Fahrenheit, or 1 degree Celsius, by 2050, and nearly 4 degrees F by 2100. That is about half the projection of global warming made a few years ago by a United Nations panel of scientists.

Based on the newer temperature estimates, the EPA report concludes that global warming is most likely to raise sea level only half as rapidly as previously estimated -- or six inches over the next 55 years, and about a foot in the next century.

"We've got a little more time," says Stephen P. Leatherman, director of coastal research at the University of Maryland at College Park. "It's not as bad as everybody thought at first, but the bad news is it's still happening."

Erosion rates around the bay vary, depending on exposure to winds and the depth of the water. The cliff in front of the Sheldons' is receding about a foot a year. An old deed shows about 70 feet of land between their house and the bay at the turn of the century.

On low-lying stretches of the Eastern Shore, the coastline is retreating up to eight feet a year, says Dr. Leatherman. Indeed, several bay islands that were once inhabited, such as Poplar and Bloodsworth, have been abandoned as they shrank.

Erosion occurs most during storms, when winds conspire with tides to push water farther inland. While a 6- or 12-inch rise in sea level may not be enough to flood coastal towns on "normal" days, it makes many areas more vulnerable to the weather.

"There's one map that shows a town like St. Michaels could even be cut in two, if you consider a hurricane surge plus a sea-level rise," says J. Court Stevenson, a wetlands ecologist at the University of Maryland's Horn Point Environmental Laboratory.

The same severe storm could turn marshy Dorchester County into the biggest island in the bay, Dr. Stevenson said. Schools in the county let out early now whenever unusually high tides threaten to flood highways.

Some experts, like Dr. Leatherman, fear that scientists' apparent backpedaling on global warming's severity will make people complacent.